Recently, with the expansion of broadcasting services supporting high definition (HD) resolution in the country and around the world, many users have been accustomed to a high resolution and definition video, such that many organizations have conducted many attempts to develop next-generation video devices. In addition, the interest in HDTV and ultra high definition (UHD) having a resolution four times higher than that of HDTV have increased and thus, a compression technology for higher-resolution and higher-definition video have been required.
Examples of the video compression technology may include an inter prediction technology predicting sample values included in a current picture from a picture before and/or after the current picture, an intra prediction technology predicting sample values included in the current picture using sample information in the current picture, a weight prediction technology for preventing deterioration of image quality due to a change in illumination, and the like, an entropy encoding technology allocating a short code to symbols having a high appearance frequency and a long code to symbols having a low appearance frequency, and the like. In particular, when the prediction for the current block is performed in a skip mode, the predicted block is generated by using only predicted values from a previously encoded region and separate motion information or a residual signal is not transmitted from an encoder to a decoder. Video data may be effectively compressed by the video compression technologies.
In order to minimize a difference between an original video and a reconstructed video at the time of encoding and decoding video, offset compensation or a loop filter may be applied. In the case of the offset compensation, and distortion from the original video can be minimized by calculating errors of sample values between the original video and the reconstructed video to obtain offsets and by applying the obtained offsets to the reconstructed video. In the case of the loop filter, the distortion from the original video can be minimized by deriving filter coefficients based on a Wiener filter minimizing errors between the original video and the reconstructed video and then, applying the derived filter coefficients to the reconstructed video.
Meanwhile, the compressed video bit streams may be transmitted through a network channel in which errors easily occur. However, when errors occur in the compressed video bit streams, the offset compensation or the loop filter according to the related art do not have the countermeasures therefore and therefore, the errors may be temporally or spatially propagated by the offset compensation or the loop filter. Therefore, the offset compensation or the loop filter according to the related art may largely degrade the image quality of the reconstructed video and the compressed video bit streams cannot be decoded.
Therefore, there is a need to apply the error-resilient offset compensation or loop filter.